Counterbalance device and torsion member usable therein

ABSTRACT

A device for counterbalancing a moving part comprises an elongated torsion member surrounded by a sleeve, the sleeve being connected to the torsion member at one point and the torsion member being fixedly supported at another point spaced from said one point, the moving part and the sleeve respectively carrying cooperating elements of a cam-follower combination, the cam being shaped, taking into account the torsion characteristics of the torsion element, to produce the desired counterbalancing effect. The torsion member itself advantageously comprises a plurality of elongated narrow elements of polygonal cross-section arranged in a predetermined grouping with sides of adjacent elements engaging one another, the exposed surfaces of said elements defining at least in part a polygonal shape, operative connections to points along the length of the torsion member being effected by bodies having appropriately shaped polygonal openings into which the grouping of the narrow elements is received so as to non-rotatably engage at least some of the elements and to confine the elements so that they are maintained in that predetermined grouping. The construction of the torsion member is such that a variety of different torsion element groupings can be received within a given polygonal opening, with a still greater variation in the number of torsion elements being possible by simple modifications of those polygonal openings, so that great latitude in operating characteristics can be achieved with an essentially standardized construction.

This application is a continuation of my earlier application Ser. No.06/477,337 of Mar. 21, 1983, now abandoned.

The present invention relates to a counterbalance device to act betweenfirst and second parts articulately connected to one another, and to aparticular torsion member construction peculiarly well-adapted for usetherein.

There are many instances where one part is articulately connected toanother so as to be movable between first and second positions, thenature of that part being such that its effective weight varies as itthus moves. For example, when a heavy lid is lifted from a horizontalposition to a vertical position, it seems heaviest at the beginning ofthat movement and its effective weight decreases as it moves toward itsvertical open position. Hence the force necessary to move it is greatestwhen the lid is horizontal and least when the lid is vertical, thuscreating a tendency to slam the lid into its vertical position and also,because of the effective weight of the lid, tending to cause the lid toslam into its horizontal position. In addition, under normalcircumstances, if the lid is released in an intermediate position itwill tend to fall back to its horizontal position, usually wtihconsiderable force. Consequently, counterbalance devices are employed,which are effective to minimize the differences in apparent weight ofthe lid as it moves from one operative position to the other, andpreferably effective to exert a force on the lid at any givenintermediate position which is substantially equal and opposite to theforce that the lid would normally exert, so that if the lid is releasedin an intermediate position it will tend to stay in that position.

Actual physical counterbalancing by means of an added and appropriatelylocated weight involves significant problems of weight, space, cost andsafety. Therefore many different artificial counterbalancing deviceshave been proposed, but few if any can produce perfect or neutralcounterbalancing (by neutral counterbalancing is meant counterbalancingsuch that the lid will remain in whatever position it finds itself, andwill exert a smooth, low resistance to movement from that position)without complex and expensive structure, and most take up a significantamount of space and add significant weight to the overall construction.Many such devices utilize hydraulic or pneumatic cylinders, which aresubject to significant maintenance problems. Springs, including torsionsprings, have been used in the past for this purpose, but they eitherare extremely bulky, heavy and expensive or they can be used only forrelatively light work. Even the bulkiest spring hinge becomes unsuitablewhen truly heavy lids are involved, and for such heavy lids the art hasturned to the use of hydraulic shock absorbers or gas springs, but theyare significantly more costly, present very substantial space problems,and obstruct side access when the lid is lifted.

Moreover, torsion spring assemblies as used in the past have involvedstructures individually designed for a particular application. When anew application calling for even a slightly different torsioncharacteristic is presented, a new and different structure must bedesigned for that purpose. This adds greatly to the cost of suchdevices. Moreover, adjustability of such structures, to accommodateexternal or internal changes or to make a given structure adaptable foruse in a plurality of environments, is difficult and unreliable.

It is a prime object of the present invention to provide neutralcounterbalancing for heavy lid-like parts, particularly those that swingabout a basically horizontal axis.

Another prime object of the present invention is to devise a torsionmember construction well adapted for use in such a counterbalance devicebut also capable of more generalized use, which torsion element issimple, reliable, inexpensive, small, light, easily manufactured, andcapable of exerting torsional resistance to light forces or quite heavyforces, all with the same basic design.

It is a further object of the present invention to device suchstructures in which a counterbalancing force or resistance to torsioncan be adjusted over a significant range without adversely affectingreliability or cost.

It is another object of the present invention to device such structureswhich can exert very substantial amounts of torque while taking up aminimal space, having minimal weight, and being significantlyinexpensive.

It is an additional object of the present invention to devise suchstructures which have a very long life and which can be readily repairedin the event that something does go wrong.

Yet a further object of the present invention is to devise suchstructures which are capable of exerting high maximum torques but whichare also "soft" in response, exerting low torques at low rotation andbuilding slowly up to high torques at high rotation.

It is a still further object of the present invention to devise suchconstructions which are simple, compact, well-protected against adverseexternal influences, which can be readily installed and removed, whichdo not obstruct access, and which are also aesthetically pleasing.

It is yet another object of the present invention to devise suchstructures which can be made from readily available material withoutrequiring high degrees of dimensional tolerance.

It is an additional object of the present invention to devise suchstructures which can be made from essentially standardized designs,which standardized designs can be readily modified to provide grossvariation in operating characteristics and which can be readily adjustedto provide fine control over operating characteristics, so that only afew standardized constructions, using standardized parts, will becapable of accommodating torques from light to very heavy.

Another object of the present invention is to provide such structureswhich, on a production basis, produce a high degree of uniformity ofspring rate, thus minimizing the need for adjustability.

In accordance with the present invention, the above and related objectsare achieved by providing the counterbalance device with an elongatedtorsion member surrounded by a sleeve. At one point the torsion memberis fixed to a support, and at another point it is non-rotatablyconnected to the sleeve. The lid or other part to be counterbalanced isprovided with one element of a cam-follower combination, the otherelement of that combination being non-rotatably connected to the sleeve.Since the torsion characteristics of the torsion member are known, andthe apparent weight-position characteristics of the lid are known, thecam can readily be shaped to impart to the system the desired overallcounterbalancing characteristics, such as, preferably, a neutralcounterbalancing. Simple, compact devices made in this fashion canaccommodate lid swings of up to 180° and exert counterbalancing torquesvarying, purely by way of example, between 0 and 500 inch pounds. Theconstruction is such that balanced torsional effects can be readilyachieved. The point along the length of the torsion member where it issecured either to the support or to the sleeve or both can be madeadjustable, thereby to modify the operating characteristics, but withoutsacrifice in the sturdiness and simplicity of the parts.

While many different types of torsion members can be employed, thetorsion member construction here disclosed and claimed is exceptionallywell suited for use in the disclosed counterbalance device, but is alsocapable of more generalized use. (Certain aspects of that torsion memberconstruction are shown in my copending application Ser. No. 422,838,filed Sept. 24, 1982, and entitled "Spring Hinge", which is assigned tothe assignee of this application.) The preferred torsion member isformed of a plurality of elongated narrow torsion elements of polygonal,and preferably essentially regular polygonal cross-section arranged in apredetermined grouping, with sides of adjacent elements engaging oneanother, the exposed surfaces of those elements defining at least inpart a polygonal shape. Nonrotative engagement with the torsion memberat a given point along its length is achieved by means of simplebushing-like parts having polygonal openings into which the grouping ofelongated torsion elements is received, the shape of those openingsbeing so related to the shape of the periphery of that grouping as tonon-rotatably engage at least some of said elements and to confine saidelements so that they are maintained in said predetermined grouping. Inmost cases the polygonal opening in a given bushing-like part is capableof receiving groups of different numbers of elongated torsion elementswithout sacrifice of the desired operating conditions, and thatcapability may be extended through the use of dummy torsion elements orother inserts. Thus a single standard construction can produce torsionmembers having widely varying torque characteristics--a grouping formedof a lesser number of elongated elements will produce a lesser torquefor a given angular displacement than will a torsion member having agreater number of such elongated elements.

Moreover, that bushing-like part in many cases can readily be slid alongthe length of the torsion member, thus varying the location of the pointwhere it engages the torsion member, thereby to vary the effectivelength of the torsion member, and hence its torque characteristic--thegreater the effective length, the less the torque that need be exertedfor a given angular displacement.

Further variation in the torque characteristics which can be producedfrom a given standardized construction is afforded through the abilityto utilize elongated narrow torsion elements of differentcross-sectional sizes in the same group.

The grouping of torsion elements is inherently exceedingly reliable andlong-lived, but its reliability may be even further enhanced bysurrounding it by a sheath of protective material, which will not onlyprotect the torsion elements against adverse external influences such asmoisture, grit or acid, but can also be used to assist in confiningthose elements to their proper locations within the grouping and toretain grease or other lubricant in position.

The points where the part to be counterbalanced and its support engagethe group of torsion elements can be appreciably spaced from oneanother, thus producing torsion members of substantial length, so thatthe possibility of overstressing of the torsion elements is minimized.Moreover, one securing point can be intermediate the length of thetorsion member, while the other points (in duplicate) are at the ends ofthe torsion member, thus producing a desirable balanced construction.

To the accomplishment of the above, and to such other objects as mayhereinafter appear, the present invention relates to a counterbalancedevice and to a torsion member construction well adapted for usetherein, as defined in the appended claims, and as described in thisspecification, taken together with the accompanying drawings in which:

FIG. 1 is a three quarter prospective view of the counterbalance deviceactive on a pivotable part, the part being shown in vertical position;

FIG. 2 is a view similar to FIG. 1 but showing the part in horizontalposition;

FIG. 3 is a cross-sectional view, on an enlarged scale, of thecounterbalance of FIG. 1, taken along the axis thereof;

FIG. 4 is a cross-sectional view taken along the line 4--4 of FIG. 3.

FIG. 5 is a cross-sectional view taken along the line 5--5 of FIG. 4 butshowing a modified structure having adjustment capability; FIG. 6 is athree quarter prospective exploded view of the parts making up thecounterbalance device of FIG. 5;

FIG. 7 is a cross-sectional view similar to FIG. 5 but showing adifferent way in which adjustability may be attained;

FIGS. 8A-E are schematic end views showing different arrangements oftorsion members of hexagonal cross-section received in hexagonalapertures of different sizes;

FIGS. 9B and C illustrate nonhexagonal apertures for receiving two orthree element torsion members respectively;

FIGS. 9D-F show different arrangements of hexagonal-cross-sectiontorsion elements in special shaped aperture configurations and,optionally, in hexagonal apertures;

FIG. 10 is a diagramatic view showing the use of hexagonal-cross-sectiontorsion elements of different diameters in a given hexagonal recess toform a torsion member;

FIG. 11 is a side elevational view of a torsion member of the presentinvention with a sheath thereover;

FIG. 12 is a side elevational view, partially broken away, of one way inwhich the sheathed torsion element of FIG. 11 may be mounted;

FIG. 13 is a view similar to FIG. 12 but showing another mountingarrangement;

FIG. 14 is an end view of the embodiment of FIG. 13 taken in thedirection of the arrows 14--14;

FIG. 15 is a view similar to FIG. 14 but showing an alternativeembodiment;

FIG. 16 is a side elevational view showing another way in which the endof the torsion member may be mounted;

FIG. 17 is a cross-sectional view taken along the line 17--17 of FIG.16;

FIG. 18 is a side elevational view, partially in cross-section, showinghow the embodiment of FIG. 11 may be mounted;

FIG. 19 is a side cross-sectional view showing the way in which thetorsion element may be mounted so that its axis can be shifted; and

FIG. 20 is a cross-sectional view taken along the line 20--20 of FIG.19.

Broadly considered, the counterbalance device of the present inventionis designed to counterbalance two articulately connected parts generallydesignated A and B, here shown more or less generically because of thewide variation possible in the nature of those parts. Part A is thefixed part, and part B is the movable part which is to becounterbalanced. Part B is pivotally connected to part A by shaft 2, thepivoting as shown being between a horizontal position for part B,corresponding to a closed lid, and a vertical position thereof,corresponding to an open lid (FIGS. 2 and 1 respectively). A portion ofpart B is broken away so that the counterbalance device can be seen whenthe part B is in its horizontal position. Part B may be of appreciableweight. When it is in its vertical position shown in FIG. 1 that weightis wholly carried by the shaft 2, so little or no force is required tomove the lid from its vertical position, but when the lid is in itshorizontal position, as shown in FIG. 2, its weight acts downwardly atpoints remote from the shaft 2, so that a considerable amount of forceis required to lift it. As the lid B is moved from its horizontal to itsvertical position, the amount of force required to move it willprogressively decrease, according to the cosine of the angle throughwhich it is moved. What is desired is to counterbalance the part B, sothat it will tend to remain in whatever position it may be placed, thecounterbalancing force equalling and opposing the effective weight ofthe part B for that particular position.

The counterbalance device of the present invention, generally designatedC, comprises an elongated torsion member generally designated D (seeFIGS. 3, 5 and 6) which, in the balanced form here shown, isnonrotatably secured adjacent its ends, at points severally designated 4and 6 respectively, to the fixed part A. The torsion member B issurrounded by a sleeve generally designated E, which is rotatablerelative to the member D and non-rotatably secured to the torsion memberD at the point generally designated 8 spaced, preferably equidistantly,from the points 4 and 6. Hence rotation of the sleeve C with respect tothe fixed support A will twist the torsion member D, and that torsionmember will therefore exert a restraining torque at least roughlyproportional to the degree to which it is twisted.

A cam-follower combination generally designated F is provided, one partof which is secured to the sleeve C and the other part of which issecured to the other part of which is secured to the part B. As heredisclosed the part B carries a cam 10 having a cam surface 12 over whicha cam follower 14 rides, the cam follower 14 being mounted on the sleeveE by means of arm 16. Because of the desirable balanced nature of theconstruction shown, with the sleeve E engaging the torsion member Dapproximately mid-way along its length and with the ends of the torsionmember D being engaged with the fixed support A, two sets ofcam-follower combinations F are provided, one at each end of the sleeveE, thus further carrying out the disclosed balanced constructionarrangement.

For securing the ends of the counterbalance devices, the fixed part A isprovided with a pair of brackets 18 secured thereto by screws 20 andeach optionally having an upper surface 22 on which the part B isadapted to rest when in its horizontal position. Secured to the brackets18, and extending inwardly therefrom, are socket members 24 having attheir inner ends inwardly extending polygonal recesses 26. Thoserecesses 26 may be of a size larger than most or all of the torsionmembers D expected to be used therewith. Received within the recess 26is an adapter 28 having a polygonal outer shape corresponding to that ofthe recess 26 so as to be non-rotatable relative to the part 24. Theinside of the adapter 28 comprises a polygonal recess 30 whichnon-rotatably receives the end of the torsion member D. When torsionmembers D of different cross-sectional sizes are used in order toproduce different torque torsion elements, the only part of theconstruction which is non-standard, but instead is directly related tothe size of the particular torsion member D, will be the adapter 28.

The sleeve E is rotatably journaled at its ends on the socket members24, and is radially spaced from the torsion member D. In order to effecta non-rotatable connection between the sleeve E and the torsion memberD, an anchor 32 having an appropriately shaped central polygonal opening34 is slid over the torsion member D to the point 8 where connection isto be made thereto. The outer surface 36 of the anchor 32 is shaped soas to snugly fit within and be slidable along the interior of the sleeveE. The non-rotative connection between the sleeve E and the anchor 32 iseffected by screw 38.

The arms 16 which carry the cam followers 14 may be of splitconstruction, with cooperating parts 42 and 44 connected by curvedlength 45 to form central bore 40 which fits snugly over the sleeve E,as may best be seen from FIGS. 4 and 6. The arm 16 may be slid intoposition along the sleeve E, the arms 42 and 44 thereof then beingclamped together by screws 46 so as to firmly non-rotatively clamp thearms 16 to the sleeve E. At their outer ends the arms 42 and 44 carrystud 48, preferably eccentric with respect to its extension 50 on whichthe cam follower 14 is journaled. This eccentricity permits a degree ofadjustment in the positioning of the cam follower 14, thereby to varythe cam action, by rotating the stud 48 within the arm 16. The cam 10 issecured to the inside of the lid B, in such a position that its camsurface 12 is engaged by the cam follower 14 when the lid is in itsvertical position as shown in FIG. 1.

In the embodiment illustrated in FIG. 3 the adapter 28 is fixed axiallywithin the part 24 in any appropriate manner, and hence the effectivedistance between the points 4 and 6 on the one hand the point 8 on theother hand remains constant, so that the resistance of the torsionmember D to twisting will remain constant. The construction shown inFIGS. 5 and 6 permits the torsional characteristics of the torsionmember D to be varied by adjustably changing the axial position of theadapter 28' of that embodiment. That adapter 28' is provided with aT-shaped slot 54 into which the head 56 projecting from screw 58 isreceived, that screw 58 being threadedly received in a tapped aperture60 in the socket member 24, the screw 58 being accessible from theexterior of the bracket 18. By turning the screw 58 and thus causing itto move axially, the associated adapter sleeve 28' will also be movedaxially, thereby moving the connecting point 4 or 6 closer to or fartherfrom the connecting point 8 and thus varying the effective length of thetorsion element D.

FIG. 7 illustrates an alternative construction for achievingadjustability. In the embodiment of FIG. 7 it is the point 8 which isshifted axially, rather than the point 4 or 6. To that end a pair ofanchors 32A and 32B are provided, each slidable axially along thetorsion member D. Each is provided with a screw 38 which passes throughan elongated slot 62 formed in the sleeve E, with a washer or the like64 pressed against the upper surface of the sleeve E by the head of thescrew 38. Hence the position of each of the anchors 32A and 32B may beadjusted axially of the torsion member D to the extent permitted by theslots 62, thereby varying the effective length of those torsion membersD.

It will be noted that in the embodiment of FIG. 7 an optional mountingof the ends of the torsion element D directly into the appropriatelyshaped openings 26 of the socket member 24 is disclosed, thuseliminating the adapter 28. This arrangement could also be used in theembodiment of FIG. 3, if the size of the torsion member D matched thesize of the opening 26. It also may be noted that the construction ofFIG. 7 readily permits the use of two separate and axially alignedtorsion members D1 and D2, each of a length approximately half thelength of the single torsion member D shown in the embodiment of FIG. 3.The screws 38 not only function to keep the anchor 32A or 32B fromsliding axially with respect to the torsion member D, but also, whenthat torsion member D is made up of a plurality of individual elements,acts to clamp the ends of those torsion elements within the anchor 32Aand thus retain the elements in position.

The torsion member D preferably comprises a plurality of elongatednarrow rods of polygonal cross-section, here shown as hexagonal incross-section. They may be made of steel or of any other structuralmaterial capable of reliably resisting torsional stresses upon repeatedapplication of those stresses. Rods functioning as torsion springs havebeen known. The greater the maximum torque to be resisted, the greaterhas been the diameter of such rods (the term "diameter" is here usedloosely to indicate maximum cross-sectional dimension, even though thecross-sectional shape is not circular), but as the diameter of the rodsincreased so did their stiffness, thus making them overly resistant tosmall forces and hence overly preventive of small movements. In thepreferred form of torsion element here disclosed, made up of a pluralityof relatively narrow rods grouped together in a particular fashion, thatdisadvantage of one piece torsion rods has been overcome--by using aplurality of rods of small cross-section grouped and mutually engagingfor simultaneous twisting, structures are obtained which are capable ofexerting extremely high torques while at the same time having arelatively "soft" reaction when low torques are applied, thus permittingslow build-up of torque with rotation and allowing large degrees oftwisting without overstressing. Moreover, the use of a plurality of suchrods permits a single standardized structure to be readily modified, forexample, by changing the number of narrow torsion elements involved, toproduce torsional characteristsics extending over a very wide range.

One accidental, but commercially very important, advantage of thisarrangement is that rods capable of use as individual torsion elementsin this application are already readily available on the market, invarious sizes, since such rods are conventionally used as Allen-headwrenches. These commercially available rods are hexagonal incross-section, which makes it exceedingly easy, from a structural pointof view, to achieve a non-rotatable rotatable relationship between atorsion element formed of such rods and the parts between torsion is tobe exerted.

FIGS. 8 through 14 are illustrative of some of these points.

FIGS. 8A and B show respectively the shapes of the openings into whichthe ends of torsion elements may be received when those elements areformed respectively of one and two rods. When three rods are employed(see FIG. 8C) the ends of the rods may be received within an hexagonalopening large enough to receive all three, with voids therearound, thevoids in this and other figures being represented by vertical shading.FIG. 8D shows the use of a larger hexagonal opening for receiving groupsof either 6 or 7 individual rods, the optional rod being indicated inthis and other drawings by horizontal shading.

FIG. 8E discloses the use of a still larger hexagonal opening forreceivng the ends of torsion elements composed of either 12 or 13 rods.

FIG. 9 is illustrative of the use of special shaped socketconfigurations to receive two rods (9B) three rods (9C), four throughseven rods (9D), six through thirteen rods (9E) or twelve throughnineteen rods (9F), the optional rods in each configuration beingindicated by horizontal shading. The configuration of the special shapedsockets is indicated by heavy lines in FIG. 9. Moreover, the 4-7 rodarrangement of FIG. 9D and the 6-13 rod arrangement of FIG. 9E can beachieved in connection with hexagonal socket configurations, asindicated by the broken peripheral lines in those figures, through theuse of inserts which fill the voids, represented in those FIGS. 8D-F bycrossed shading.

FIG. 10 illustrates another way in which variation in torquecharacteristics can be achieved with a given socket configuration. Inthe embodiment of FIG. 14 six relatively large cross-section rods arereceived within the socket configuration, from one to six smallercross-section rods may optionally be employed at the periphery, and inaddition either one large sized rod or three small sized rods may beemployed at the center. Since if a rod has twice the diameter, it issixteen times as stiff, variation of stiffness in this manner isachieved.

It is also possible, as disclosed more in detail in my previouslyreferred to application Ser. No. 422,838 entitled "Spring Hinge", topartially fill the socket opening with dummy rods, rods which do notextend to the other point of connection. Only those rods which extendbetween the two points of connection, and which therefore are twistedwhen those points have relative rotation imparted to them, contribute tothe torque effect.

Once the ends of the rods are properly grasped in a socket, the rodswill tend to be reliably held together, but when the sockets areseparated from one another by an appreciable distance some additionalmeans may be desired to retain the individual rods in their bundle.Moreover, it is often desired to insulate the rods from external adverseeffects, such as water, dirt or acid, and it is sometimes advantageousto retain grease or other lubricant on the rods over their length. Toaccomplish that, as shown in FIG. 11, a sheath 64 may be provided overthe bundle of rods, which sheath may be formed from a heat-shrinkableplastic material. As shown in FIGS. 12 and 13, when the ends of thetorsion member D are received in socket members such as the members 24Aand 24B of FIGS. 16 and 17 respectively, the ends 64A of the sheath 64may be shrunk over the socket members, thus sealing the torsion member Dquite effectively.

FIGS. 12-20 are illustrative of different ways in which the ends of thetorsion member D may be connected to a part with which they are to beassociated. In FIG. 12 the socket member 24A is mounted in an aperture66 on a supporting plate 68 and is secured thereto by screws 70. In theembodiment of FIG. 13 the socket member 24B is provided at its end withan opening 72, two different embodiments of which are shown in FIGS. 14and 15 respectively, which openings are adapted to receive matinglyshaped operative elements such as shaft ends.

FIGS. 16 and 17 illustrate another type of mounting, in which the end ofthe torsion member D is received in a socket member 24C which isprovided on its outer surface with knurling 74, so that it can be slidinto an appropriately internally knurled operating element.

FIG. 18 shows a socket member 24D which is welded to a supportingelement 68 and into which the end of the torsion member D is slidable,the socket member 24D having an hexagonal socket opening 76corresponding to the size and shape of the bundle of individual torsionrods.

FIGS. 19 and 20 show how the torsion member D can be mounted in anon-perpendicular position with respect to the supporting element 68.That element is provided with a socket member 78 having an hexagonalsocket opening 80. The end of the torsion member D is fixedly mounted toa head 82 which, as may be seen in FIG. 20, is hexagonal when viewed inthe direction of its axis but which is ball-shaped when viewed from theside.

The conventional way to counterbalance a moving part is to provide aweight connected to that part but located on the opposite side of thepivotal axis, thereby to provide literal counterbalance. However, thatapproach is costly in material, significantly adds to the weight of theoverall device, takes up considerable space, and is a safety hazard.Through the use of the counterbalance of the instant invention, however,no additional space is required and effective counterbalancing isachieved. Significantly, this can be done even though the maximum torquerequirements may be quite high, 500 inch pounds or higher. Closeapproximation to the counterbalancing that is required in a giveninstallation can be achieved through the use of the proper torsionelement, such adjustment in the operative characteristics of thattorsion element as are required may be achieved in a simple fashion, andthen extremely accurate control of the final torque characteristics isachieved through simple cam design. The cam and spring function togetherto produce the desired counterbalanc effect. The counterbalance can belocated off the axis of the movable part, through the use of a flexibleshaft connection. The structure can be adapted to virtually any spacingon the customer's equipment--there can be dead space in the center ofthe counterbalance device when the spacing required by the customer isgreat, or, if the space required by the customer is small, an end of thecounterbalance device can extend out laterally beyond the part beingcontrolled. Balanced spring and cam action can be accomplished with buta single torsion element. Not only can the cam be shaped to produce anydesired torsional response, but even a detent action can be obtained ifdesired simply by modifying the cam shape. Damping can be easilyachieved simply by adding friction to the cam follower, but if that camfollower is relatively friction-free on the shaft on which it ismounted, the unit has very little hysteresis.

By forming the torsion member from a plurality of elongated polygonalrods formed into a bunch and mounted as disclosed, many advantagesderive. For a given torque output characteristic, that arrangement takesup less weight and has a smaller diameter than a comparable coil spring,and will work in both rotative directions, whereas a coil spring willnot. Over a single torsion bar it has the advantage that it can be muchshorter while producing the desired degree of softness, and will allowmuch greater rotation without overstressing. Moreover, a wide variety oftorsion characteristics can be achieved with the use of standardizedconstruction. Although non-precision parts are involved, the torqueoutput characteristics are quite uniform. There is a high consistency inproduction. The units are reliable, and very easily repaired. Theindividual rods are connected in parallel, so if one does break becauseof fatigue there is no catastrophic failure. Moreover, because of theuse of a plurality of rods it is mot unlikely that any given rod willbecome overstressed. The torsion member is extremely silent inoperation, and the bunch of rods can be sealed against the environment.Nonrotative connections to the torsion member are easy to make becauseof its non-circular external configuration.

For a given amount of longitudinal space, this arrangement gives softerspring rates for a given load, and has greater angular travel capabilityfor a given load, than other types of springs. The unit can be shorterthan other units, and selection of a desired number of torsion rodsprovides many small increments in operating characteristics.

An important factor is that the spring elements are not subjected tosurge problems, which normally lead to unequal load distribution,excessive wear and oscillation.

While several embodiments of the present invention have been heredisclosed, it will be apparent that they are but exemplary of othervariations which could be made therein, all within the scope of theinvention as defined in the following claims:

I claim:
 1. A counterbalance device to act between first and secondparts connected to one another to pivot about a first axis, comprising apair of spaced supports adapted to be secured to said first part andspaced from one another along a second axis spaced from said first axis,socket members secured to said supports, extending toward one another,and having polygonal recesses facing one another along said second axis,a torsion member having ends non-rotatably received in said recesses andextending along said second axis, a sleeve extending between and mountedon said socket members to rotate relative to said socket members aboutsaid second axis, said torsion member being freely received within saidsleeve, an anchor means inside said sleeve .[.non-rotatably mounted onsaid torsion member at a point spaced from said socket members, andmeans operatively connecting said anchor means to said second part.]..Iadd.and non-rotatably connected to said sleeve and to said torsionmember at a first point spaced from said socket members, and meansexternally non-rotatably mounted on said sleeve at a second pointaxially spaced from said first point and operatively connecting saidsleeve to said second part.Iaddend..
 2. In the counterbalance device ofclaim 1, adaptors non-rotatably received in said socket member recessesand having polygonal second recesses facing one another along saidsecond axis, the ends of said torsion member being non-rotativelyreceived in said second recesses.
 3. The counterbalance of either ofclaims 1 or 2, in which said anchor means is axially adjustably slidableon said torsion member and is located approxiomately midway between saidsocket members.
 4. The counterbalance of either of claims 1 or 2, inwhich said sleeve has a central aperture, said anchor means has aperiphery generally corresponding to said central aperture to thereby beaxially slidably adjustable within said sleeve, said anchor means havinga polygonal through opening, and said torsion member is slidably butnon-rotatively received within said central through opening, said anchormeans being located approximately midway between said socket members..[.5. In the counterbalanc of either of claims 1 or 2, said means foroperatively connecting said anchor means to said second part comprisingmeans non-rotatably connecting said sleeve and said anchor means, andmeans operatively connecting said sleeve to said second part..].
 6. Acounterbalance device to act between first and second parts articulatelyconnected to one another, comprising a pair of spaced supports adaptedto be secured to said first part, socket members secured to saidsupports, extending toward one another, and having facing polygonalrecesses, longitudinally extending lengths of torsion member each havingan end nonrotatably received in said recesses respectively, a sleeveextending between and rotatably mounted on said socket members withinwhich said torsion member is freely received, anchor means inside saidsleeve non-rotatably mounted on said lengths of torsion members at.Iadd.first .Iaddend.points spaced from said socket membersrespecctively, an arm extending radially from and non-rotatably securedto said sleeve .Iadd.at a point axially spaced from said firstpoints.Iaddend., a cam adapted to be secured to said second partradially spaced from said sleeve, cam follower means on said armengaging said cam, and means non-rotatably connecting said sleeve andsaid anchor means, said torsion member exerting a rotary force on saidsleeve in a direction to urge said follower against said cam.
 7. Thecounterbalance device of claim 6, in which said torsion member lengthsare defined by a single longitudinally continuous structure.
 8. Thecounterbalance device of claim 6, in which said first and second partsare connected to one another to pivot about a first axis, said torsionmember and said sleeve extending along a second axis radially spacedfrom said first axis.
 9. The counterbalance of either of claims 6 or 8,in which there are two sets of arms, cams and cam followers axiallyspaced from one another along the axis of said sleeve.
 10. Thecounterbalance of either of claims 6 or 8, in which there are two setsof arms, cams and cam followers axially spaced from one another alongthe axis of said sleeve and axially spaced from said anchor means. 11.The counterbalance of either of claims 6 or 8, in which there are twosets of arms, cams and cam followers axially spaced from one anotheralong the axis of said sleeve and axially spaced from said anchor means,said arms being axially adjustably positionable along said sleeve. 12.The counterbalance of either of claims 6 or 8, in which there are twosets of arms, cams and cam followers axially spaced from one anotheralong the axis of said sleeve, said arms being axially adjustablypositionable along said sleeve.
 13. In the counterbalance device ofeither of claims 6 or 8, adaptors non-rotatably received in said socketmember recesses and having polygonal second recesses facing one another,the ends of said torsion member being non-rotatably received in saidsecond recesses.
 14. A mechanism including a first member and a secondmember and a pivotal connection securing said members together forrelative movement about a pivotal axis, and a torsion-spring mechanismfor providing spring bias between said members about said pivotal axis,said torsion-spring mechanism including(a) first and second bearingssecured to said first member at spaced-apart locations, said first andsecond bearings being mutually aligned along a torsion spring axisparallel to said pivotal axis, (b) an elongated tube coaxial with saidtorsion spring axis and having opposite ends pivotally supported by saidfirst and second bearings, respectively, (c) an elongated torsion springunit extending along said torsion spring axis and contained in saidtube, said first bearing including means for fixing a first portion ofsaid torsion spring unit at an end thereof against turning about saidtorsion spring axis relative to said first member, and means acting on asecond portion of said torsion spring unit spaced substantially alongsaid torsion spring axis from said first bearing for securing saidsecond portion against turning relative to said tube, and (d) cam meansincluding a cam secured to said second member and a cooperatingcam-follower arm projecting from said tube and secured thereto forapplying spring bias between said first and second members as developedby said torsion spring unit and modified by said cam means.Iadd., (e)said cam-follower arm being located on said tube at a point axiallyspaced from said means acting on a second portion of said torsionspring.Iaddend..
 15. A mechanism as in claim 14, wherein said elongatedtorsion spring unit has a third portion at the end of said unit remotefrom said first portion and spaced substantially along said torsionspring axis from said second portion, wherein said second bearingincludes means for fixing said third portion of the torsion spring unitagainst turning about the torsion spring axis relative to said firstmember.
 16. A mechanism as in claim 14, further including a secondelongated torsion spring unit contained in said tube, said secondbearing including means fixing a first portion of said second torsionspring unit against turning about said torsion spring axis relative tosaid first member, and means acting on a second portion of said secondtorsion spring unit spaced substantially from said second bearing forsecuring said second portion of said second torsion spring unit againstturning relative to said tube. A mechanism as in claim 14 wherein saidelongated torsion spring unit comprises a bundle of rods each of whichhas a regular polygonal cross-section and wherein each of said means forsecuring said first and second portions against turning includes arespective socket having a cavity that receives a respective portion ofthe bundle of rods, the cross-section of each cavity having facets thatbear against respective facets of at least certain of the polygonalrods.
 18. A mechanism as in claim 15, wherein said elongated torsionspring unit comprises a bundle of rods each of which has a regularpolygonal cross-section and wherein each of said means for securing saidfirst, second and third portions of the torsion spring unit againstturning includes a respective socket having a cavity that receives arespective portion of the bundle of rods, the cross-section of eachcavity having facets that bear against respective facets of at leastcertain of the polygonal rods.
 19. A mechanism as in claim 16, whereineach of said torsion spring units comprises a bundle of rods each ofwhich has a regular polygonal cross-section and wherein the means forsecuring each of the first and second portions of each of said torsionspring units, respectively, against turning includes a respective sockethaving a cavity that receives a respective portion of one of saidbundles of rods, the cross-section of each cavity having facets thatbear against respective facets of certain of the polygonal rods.
 20. Amechanism as in any of claims 14-16, wherein said cam means includes asecond cam secured to said second member and a second cooperatingcam-follower arm projecting from said tube and secured thereto, said camand its cooperating cam follower being spaced along said tube far fromsaid second cam and said second cam follower in a balanced constructionwherein said cam-follower arms are constrained by said tube to move incoordination with each other.
 21. A torsion spring device including anelongated tube, a pair of bearing members aligned with each other alongthe axis of the tube and cooperating with opposite ends of said tube toprovide bearing support for the tube, said bearings being adapted to besecured non-rotatably to an external member, said members havingrespective sockets that provide cavities opening toward each other,torsion spring means comprising bundled rods of regular polygonalcross-section extending axially inside said tube and having opposite endportions received non-rotatably in the cavities of said sockets, meansdisposed between and spaced substantially from both of said sockets forsecuring said tube to said bundled rods, thereby developing two lengthsof bundled rods extending between said tube and said sockets, and meanssecured to said tube for developing torsion in said bundled rods.Iadd.,said means being secured to said tube at a point axially spaced fromsaid means for securing said tube to said bundled rods.Iaddend..
 22. Atorsion spring device as in claim 21, wherein said bundled rods extendcontinuously between said opposite end portions and wherein said meansfor securing said tube to said bundled rods comprises at least onemember fixed nonrotatably to said tube and having a passage throughwhich said bundled rods extend nonrotatably relative to said tube.
 23. Atorsion spring device as in claim 21, wherein said bundled rods aredivided into two endwise aligned torsion spring units each having an endportion received in a respective one of said sockets as aforesaid, andwherein said means for securing said tube to said bundled rods comprisesa pair of anchor members secured non-rotatably to said tube and each ofsaid anchor members having an opening that receives non-rotatably aportion of a respective one of said torsion spring units.